1. Field of the Invention
The present invention relates to polymer composite materials with biocide functionality, methods for producing such polymer composite materials and their use, in particular for agriculture.
2. Description of Related Art
A wide variety of polymer materials like biodegradable mulch films for reducing weed growth or special biodegradable horticulture pots are known which are used in the field of agriculture. An emphasis in the equipment of these polymer materials lies in the task either to stabilize the material against environmental and chemical influences or to improve the biodegradability of the material. Examples for agricultural films stabilized against pesticides with an additive can be found in Japanese application JP 631 75 072. In the European patent application EP 0214507 there are UV stabilizers described which are used in films for outdoor agriculture.
An example of a material capable of thermal diffusion of an active ingredient is described in DE 28 19 515 A1. A multilayered composite material comprises a layer which is able to increase the temperature within the material by exothermic chemical reaction so that a functional material can be set free. However, the disclosed inorganic chemical substances which are needed for the exothermic reaction are harmful to the environment as well as unsuitable for the production, harvest or transport of food and medical articles.
Another polymer material incorporating biocide inorganic substances is known from DE 696 29 891 T2. There, chlorine dioxide is provided as biocide inorganic substance to act as a disinfectant in films for food packaging. However, the handling and controlling of the right amount of disinfectant over a given time period is difficult complex and costly. According to the disclosed material it involves different layers which must include a hydrophobic layer comprising an acid freeing substance and a neighbouring hydrophilic layer comprising chlorinate ions.
Another approach to functionalize agricultural or horticultural polymers lies in the incorporation of inorganic substances like copper, copper salts and finely pulverized silver acting as disinfectants. However, the release of the active substance is incontrollable and often involves the degradation or dissolving of the polymer.
All yet known polymer materials in agriculture or horticulture share the problem that the lifespan of the functionalized material is short. Moreover, the function often only lies in the protection of the polymer itself. However, a function for the agricultural goods like that of a biocide is not given in a convenient way because of the limitation to only inorganic substances, again involving degradable or soluble polymers to set free the inorganic substance. Like that, a lifespan required for a growing season of 12 months or in case of reuse of several years and/or over several planting and harvesting seasons of the functionalized polymer material is impossible. The mechanical properties decrease over time with increasing biodegradation causing a molecular weight reduction of the polymer. Molecular weight reduction reducing desired polymer performance like strength necessary for mitigation of weather fluctuations by agricultural films or protecting the roots of seedlings by nursery pots and trays, for example.